From patchwork Tue Sep 12 11:57:27 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= X-Patchwork-Id: 722276 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30C7FCA0EC3 for ; Tue, 12 Sep 2023 11:59:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235022AbjILL7M (ORCPT ); Tue, 12 Sep 2023 07:59:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234978AbjILL6U (ORCPT ); Tue, 12 Sep 2023 07:58:20 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C66131981; Tue, 12 Sep 2023 04:58:01 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30E0BC433C7; Tue, 12 Sep 2023 11:57:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1694519881; bh=G3ZQqiwe5gyTFzZ+daR1X2GrYG5m5yMSRJlV8uyElWE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=N9waNLu43RFFaehAC2n7+UH532/KbktpyyUI5X4q9mkeuMBcnRYayjmZetCZt/gbv KbY+tNF613mLp/gYnys/+D2vN13XmCS4e3aDnOjY9Xy7pgvUUz3UcCdSGnoNWNFgEN zSqTfJ56Y4/gIhE22VFdx3QfCxyDAvZQpdSAoK1ymsPfxcjdZrW/wsmmKy9r3AoTlT dPyljxaiQO0uLPQGsB6zioThmZOXDLPjtSTbOhOiUN20Xx9Hq9QnNTDgIwiyNBP6Br KSLoRFPUZuqT/zd5r06UTfaV3WUjBdKoowgmgFXuW3qoLl4trKIz+ZzguGO7bpsOqA 2PqjCXdRT2fzA== From: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= To: Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-riscv@lists.infradead.org, Andy Chiu , Greentime Hu , "Jason A . Donenfeld" , Samuel Neves Cc: Heiko Stuebner , Herbert Xu , "David S. Miller" , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 5/6] riscv: vector: allow kernel-mode Vector with preemption Date: Tue, 12 Sep 2023 13:57:27 +0200 Message-Id: <20230912115728.172982-6-bjorn@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230912115728.172982-1-bjorn@kernel.org> References: <20230912115728.172982-1-bjorn@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org From: Andy Chiu Add kernel_vstate to keep track of kernel-mode Vector registers when trap introduced context switch happens. Also, provide trap_pt_regs to let context save/restore routine reference status.VS at which the trap takes place. The thread flag TIF_RISCV_V_KERNEL_MODE indicates whether a task is running in kernel-mode Vector with preemption 'ON'. So context switch routines know and would save V-regs to kernel_vstate and restore V-regs immediately from kernel_vstate if the bit is set. Apart from a task's preemption status, the capability of running preemptive kernel-mode Vector is jointly controlled by the RISCV_V_VSTATE_CTRL_PREEMPTIBLE mask in the task's thread.vstate_ctrl. This bit is masked whenever a trap takes place in kernel mode while executing preemptive Vector code. Also, provide a config CONFIG_RISCV_ISA_V_PREEMPTIVE to give users an option to disable preemptible kernel-mode Vector at build time. Users with constraint memory may want to disable this config as preemptible kernel-mode Vector needs extra space for tracking per thread's kernel-mode V context. Or, users might as well want to disable it if all kernel-mode Vector code is time sensitive and cannot tolerate context swicth overhead. Signed-off-by: Andy Chiu --- arch/riscv/Kconfig | 10 +++++ arch/riscv/include/asm/processor.h | 2 + arch/riscv/include/asm/simd.h | 4 +- arch/riscv/include/asm/thread_info.h | 4 ++ arch/riscv/include/asm/vector.h | 27 +++++++++++-- arch/riscv/kernel/asm-offsets.c | 2 + arch/riscv/kernel/entry.S | 45 ++++++++++++++++++++++ arch/riscv/kernel/kernel_mode_vector.c | 53 ++++++++++++++++++++++++-- arch/riscv/kernel/process.c | 8 +++- arch/riscv/kernel/vector.c | 3 +- 10 files changed, 148 insertions(+), 10 deletions(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index d607ab0f7c6d..dc51164b8fd4 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -520,6 +520,16 @@ config RISCV_ISA_V_DEFAULT_ENABLE If you don't know what to do here, say Y. +config RISCV_ISA_V_PREEMPTIVE + bool "Run kernel-mode Vector with kernel preemption" + depends on PREEMPTION + depends on RISCV_ISA_V + default y + help + Ordinarily the kernel disables preemption before running in-kernel + Vector code. This config frees the kernel from disabling preemption + by adding memory on demand for tracking kernel's V-context. + config TOOLCHAIN_HAS_ZBB bool default y diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h index 3e23e1786d05..f9b85e37e624 100644 --- a/arch/riscv/include/asm/processor.h +++ b/arch/riscv/include/asm/processor.h @@ -82,6 +82,8 @@ struct thread_struct { unsigned long bad_cause; unsigned long vstate_ctrl; struct __riscv_v_ext_state vstate; + struct pt_regs *trap_pt_regs; + struct __riscv_v_ext_state kernel_vstate; }; /* Whitelist the fstate from the task_struct for hardened usercopy */ diff --git a/arch/riscv/include/asm/simd.h b/arch/riscv/include/asm/simd.h index ef70af78005d..a54a0ce58f4d 100644 --- a/arch/riscv/include/asm/simd.h +++ b/arch/riscv/include/asm/simd.h @@ -12,6 +12,7 @@ #include #include #include +#include #ifdef CONFIG_RISCV_ISA_V @@ -35,7 +36,8 @@ static __must_check inline bool may_use_simd(void) * where it is set. */ return !in_irq() && !irqs_disabled() && !in_nmi() && - !this_cpu_read(vector_context_busy); + !this_cpu_read(vector_context_busy) && + !test_thread_flag(TIF_RISCV_V_KERNEL_MODE); } #else /* ! CONFIG_RISCV_ISA_V */ diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h index b182f2d03e25..8797d520e8ef 100644 --- a/arch/riscv/include/asm/thread_info.h +++ b/arch/riscv/include/asm/thread_info.h @@ -94,6 +94,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); #define TIF_UPROBE 10 /* uprobe breakpoint or singlestep */ #define TIF_32BIT 11 /* compat-mode 32bit process */ #define TIF_RISCV_V_DEFER_RESTORE 12 /* restore Vector before returing to user */ +#define TIF_RISCV_V_KERNEL_MODE 13 /* kernel-mode Vector run with preemption-on */ #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) @@ -101,9 +102,12 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL) #define _TIF_UPROBE (1 << TIF_UPROBE) #define _TIF_RISCV_V_DEFER_RESTORE (1 << TIF_RISCV_V_DEFER_RESTORE) +#define _TIF_RISCV_V_KERNEL_MODE (1 << TIF_RISCV_V_KERNEL_MODE) #define _TIF_WORK_MASK \ (_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED | \ _TIF_NOTIFY_SIGNAL | _TIF_UPROBE) +#define RISCV_V_VSTATE_CTRL_PREEMPTIBLE 0x20 + #endif /* _ASM_RISCV_THREAD_INFO_H */ diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h index 9b818aac8a94..9fb2dea66abd 100644 --- a/arch/riscv/include/asm/vector.h +++ b/arch/riscv/include/asm/vector.h @@ -196,9 +196,24 @@ static inline void __switch_to_vector(struct task_struct *prev, { struct pt_regs *regs; - regs = task_pt_regs(prev); - riscv_v_vstate_save(&prev->thread.vstate, regs); - riscv_v_vstate_set_restore(next, task_pt_regs(next)); + if (IS_ENABLED(CONFIG_RISCV_ISA_V_PREEMPTIVE) && + test_tsk_thread_flag(prev, TIF_RISCV_V_KERNEL_MODE)) { + regs = prev->thread.trap_pt_regs; + WARN_ON(!regs); + riscv_v_vstate_save(&prev->thread.kernel_vstate, regs); + } else { + regs = task_pt_regs(prev); + riscv_v_vstate_save(&prev->thread.vstate, regs); + } + + if (IS_ENABLED(CONFIG_RISCV_ISA_V_PREEMPTIVE) && + test_tsk_thread_flag(next, TIF_RISCV_V_KERNEL_MODE)) { + regs = next->thread.trap_pt_regs; + WARN_ON(!regs); + riscv_v_vstate_restore(&next->thread.kernel_vstate, regs); + } else { + riscv_v_vstate_set_restore(next, task_pt_regs(next)); + } } void riscv_v_vstate_ctrl_init(struct task_struct *tsk); @@ -223,4 +238,10 @@ static inline bool riscv_v_vstate_ctrl_user_allowed(void) { return false; } #endif /* CONFIG_RISCV_ISA_V */ +#ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE +void kernel_vector_allow_preemption(void); +#else +#define kernel_vector_allow_preemption() do {} while (0) +#endif + #endif /* ! __ASM_RISCV_VECTOR_H */ diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c index d6a75aac1d27..4b062f7741b2 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -38,6 +38,8 @@ void asm_offsets(void) OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count); OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp); OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp); + OFFSET(TASK_THREAD_TRAP_REGP, task_struct, thread.trap_pt_regs); + OFFSET(TASK_THREAD_VSTATE_CTRL, task_struct, thread.vstate_ctrl); OFFSET(TASK_THREAD_F0, task_struct, thread.fstate.f[0]); OFFSET(TASK_THREAD_F1, task_struct, thread.fstate.f[1]); diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 143a2bb3e697..b6a7d4e9f526 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -66,6 +66,29 @@ _save_context: REG_S s4, PT_CAUSE(sp) REG_S s5, PT_TP(sp) +#ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE + /* + * Record the register set at the frame where in-kernel V registers are + * last alive. + */ + REG_L s0, TASK_TI_FLAGS(tp) + li s1, 1 << TIF_RISCV_V_KERNEL_MODE + and s0, s0, s1 + beqz s0, 1f + li s0, TASK_THREAD_TRAP_REGP + add s0, s0, tp + REG_L s1, (s0) + bnez s1, 1f + REG_S sp, (s0) + li s0, TASK_THREAD_VSTATE_CTRL + add s0, s0, tp + REG_L s1, (s0) + li s2, ~RISCV_V_VSTATE_CTRL_PREEMPTIBLE + and s1, s1, s2 + REG_S s1, (s0) +1: +#endif + /* * Set the scratch register to 0, so that if a recursive exception * occurs, the exception vector knows it came from the kernel @@ -129,6 +152,28 @@ SYM_CODE_START_NOALIGN(ret_from_exception) */ csrw CSR_SCRATCH, tp 1: +#ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE + /* + * Clear tracking of the trap registers when we return to the frame + * that uses kernel mode Vector. + */ + REG_L s0, TASK_TI_FLAGS(tp) + li s1, 1 << TIF_RISCV_V_KERNEL_MODE + and s0, s0, s1 + beqz s0, 1f + li s0, TASK_THREAD_TRAP_REGP + add s0, s0, tp + REG_L s1, (s0) + bne s1, sp, 1f + REG_S x0, (s0) + li s0, TASK_THREAD_VSTATE_CTRL + add s0, s0, tp + REG_L s1, (s0) + ori s1, s1, RISCV_V_VSTATE_CTRL_PREEMPTIBLE + REG_S s1, (s0) +1: +#endif + REG_L a0, PT_STATUS(sp) /* * The current load reservation is effectively part of the processor's diff --git a/arch/riscv/kernel/kernel_mode_vector.c b/arch/riscv/kernel/kernel_mode_vector.c index d9e097e68937..5c64f2034cdc 100644 --- a/arch/riscv/kernel/kernel_mode_vector.c +++ b/arch/riscv/kernel/kernel_mode_vector.c @@ -10,6 +10,7 @@ #include #include #include +#include #include #include @@ -48,6 +49,44 @@ static void put_cpu_vector_context(void) preempt_enable(); } +#ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE +void kernel_vector_allow_preemption(void) +{ + current->thread.vstate_ctrl |= RISCV_V_VSTATE_CTRL_PREEMPTIBLE; +} + +static bool kernel_vector_preemptible(void) +{ + return !!(current->thread.vstate_ctrl & RISCV_V_VSTATE_CTRL_PREEMPTIBLE); +} + +static int riscv_v_start_kernel_context(void) +{ + struct __riscv_v_ext_state *vstate; + + vstate = ¤t->thread.kernel_vstate; + if (!vstate->datap) { + vstate->datap = kmalloc(riscv_v_vsize, GFP_KERNEL); + if (!vstate->datap) + return -ENOMEM; + } + + current->thread.trap_pt_regs = NULL; + WARN_ON(test_and_set_thread_flag(TIF_RISCV_V_KERNEL_MODE)); + return 0; +} + +static void riscv_v_stop_kernel_context(void) +{ + WARN_ON(!test_and_clear_thread_flag(TIF_RISCV_V_KERNEL_MODE)); + current->thread.trap_pt_regs = NULL; +} +#else +#define kernel_vector_preemptible() (false) +#define riscv_v_start_kernel_context() (0) +#define riscv_v_stop_kernel_context() do {} while (0) +#endif /* CONFIG_RISCV_ISA_V_PREEMPTIVE */ + /* * kernel_vector_begin(): obtain the CPU vector registers for use by the calling * context @@ -70,11 +109,14 @@ void kernel_vector_begin(void) riscv_v_vstate_save(¤t->thread.vstate, task_pt_regs(current)); - get_cpu_vector_context(); + if (!preemptible() || !kernel_vector_preemptible()) { + get_cpu_vector_context(); + } else { + if (riscv_v_start_kernel_context()) + get_cpu_vector_context(); + } riscv_v_enable(); - - return 0; } EXPORT_SYMBOL_GPL(kernel_vector_begin); @@ -96,6 +138,9 @@ void kernel_vector_end(void) riscv_v_disable(); - put_cpu_vector_context(); + if (!test_thread_flag(TIF_RISCV_V_KERNEL_MODE)) + put_cpu_vector_context(); + else + riscv_v_stop_kernel_context(); } EXPORT_SYMBOL_GPL(kernel_vector_end); diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index ec89e7edb6fd..18cb37c305ab 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -160,8 +160,11 @@ void flush_thread(void) void arch_release_task_struct(struct task_struct *tsk) { /* Free the vector context of datap. */ - if (has_vector()) + if (has_vector()) { kfree(tsk->thread.vstate.datap); + if (IS_ENABLED(CONFIG_RISCV_ISA_V_PREEMPTIVE)) + kfree(tsk->thread.kernel_vstate.datap); + } } int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) @@ -170,7 +173,9 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) *dst = *src; /* clear entire V context, including datap for a new task */ memset(&dst->thread.vstate, 0, sizeof(struct __riscv_v_ext_state)); + memset(&dst->thread.kernel_vstate, 0, sizeof(struct __riscv_v_ext_state)); clear_tsk_thread_flag(dst, TIF_RISCV_V_DEFER_RESTORE); + clear_tsk_thread_flag(dst, TIF_RISCV_V_KERNEL_MODE); return 0; } @@ -205,6 +210,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) childregs->a0 = 0; /* Return value of fork() */ p->thread.s[0] = 0; } + kernel_vector_allow_preemption(); p->thread.ra = (unsigned long)ret_from_fork; p->thread.sp = (unsigned long)childregs; /* kernel sp */ return 0; diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c index 9d583b760db4..42f227077ee5 100644 --- a/arch/riscv/kernel/vector.c +++ b/arch/riscv/kernel/vector.c @@ -122,7 +122,8 @@ static inline void riscv_v_ctrl_set(struct task_struct *tsk, int cur, int nxt, ctrl |= VSTATE_CTRL_MAKE_NEXT(nxt); if (inherit) ctrl |= PR_RISCV_V_VSTATE_CTRL_INHERIT; - tsk->thread.vstate_ctrl = ctrl; + tsk->thread.vstate_ctrl &= ~PR_RISCV_V_VSTATE_CTRL_MASK; + tsk->thread.vstate_ctrl |= ctrl; } bool riscv_v_vstate_ctrl_user_allowed(void)